Ebonite or hard-rubber linings have been used for decades for protecting metals from corrosion or chemical attack as documented in “Corrosion Prevention by Protective Coatings, Second Edition, Chapter 20,” by Charles Munger, 1999 (Publisher: National Association of Corrosion Engineers). Such linings are applied in sheets and require adhesive bonding to the metal surface as well as at the overlays. The application is craft sensitive and time consuming.
To overcome the disadvantages of the ebonite or hard-rubber linings, several single-component liquid rubber based ebonite coatings have also been disclosed by Rappoport in U.S. Pat. No. 5,766,687 and U.S. Pat. No. 5,997,953, by Figovsky in WO 0,006,639, and by Petrovic et al. in DE 3,740,181. These liquid coatings can be rolled, brushed, trowelled or sprayed onto the metal surface to form a monolithic layer, thus simplifying the application.
However, these single component ebonite coatings still suffer from two major drawbacks. First, they will sag, drip, flow or run off on a non-horizontal surface when subjected to the subsequent heating during the vulcanization stage and result in uneven coating, which compromises its protective function. Second, their surface is tacky, making it difficult for multiple coats.
To overcome the run-off problem and to achieve a tack free surface to facilitate handling, Chang et al. in U.S. Pat. No. 6,482,894 disclosed a two-component liquid ebonite coating system. The second component is based on an unsaturated liquid rubber which contains a functional group capable of reacting with the functional group in the first component at room temperature. When the two components are mixed and applied, e.g. by spraying, onto a metal substrate, the coating will gel at the room temperature and thus prevents run-off during the subsequent vulcanization stage. Hoelter et al. in U.S. Pat. Application 2002/0002244 also proposed a two component coating system, with the second component being mainly low molecular weight polyisocyanates. Although the two-component liquid ebonite coatings solved the run-off problem, the two component coating system of Hoelter et al. requires an extra step of mixing the two components before application onto the metal substrate.
To overcome the shortcomings of aforementioned various linings and coatings, the present invention discloses a single-component moisture activated liquid ebonite coating that does not require premixing and does not sag or run off.